Near-field recording techniques have been developed that advantageously attain the storage capacity of high-end tape drives and libraries with the seek time and transfer rate performance and costs comparable to mid-range hard-disk drives. Near-field recording systems combine technology of several fields including magnetic recording, optical recording, magneto-optical (M-O) systems, consumer electronics, and microscopy to attain improvements in areal density, capacity, performance, and cost.
One technology that is highly useful for storing large quantities of data is optical data mass storage in which data is accessed by focusing a laser beam onto a data surface of the disc and detecting light reflected from or transmitted through the data surface. For a typical optical mass storage disk, stored data is arranged in tracks arranged on a reflective surface of the disk. To read the data from a selected track, optics in an optical disk drive generate a beam of light, for example a laser beam, and direct the beam toward the selected track where the beam is reflected. Data stored on the disk is reconstructed during a read operation by monitoring the beam after reflection. Read and write optics generally include a moveable mirror or lens to precisely guide the beam to the selected track, and an objective lens located near the reflective surface to focus the beam upon the surface.
A near-field recording head operates as a flying head that is positioned a xe2x80x9cnear-fieldxe2x80x9d distance from a recording media of less than the wave-length of the interrogating laser light. One type of recording component is a solid immersion lens (SIL) which is used to focus a laser beam to a fine spot. To write to an optical media, energy from the fine spot is transferred or coupled onto a surface of a disk medium in an effect called xe2x80x9cevanscent couplingxe2x80x9d. The near-field recording head uses a tiny magnetic coil that writes information to the heated spot on the disk. Ultra-small bit domains are written to overlapping sequences, creating a series of bit domains that are generally in the shape of a crescent. Usage of crescent-shaped bit domain recording effectively doubles the bit density, increasing overall areal density.
During a write operation, laser energy that is transferred by the flying head to the media heats a spot on the recording surface to a Curie point of about 300xc2x0 C. in roughly one nanosecond. A magnetic field is pulsed into the heated spot by a planar coil embedded within the head substrate. The planar coil is generally a flat coil that rests in a plane parallel to the plane of the flying head surface. The planar coil is very small and light-weight and typically is formed within the flying head assembly, rather than exposed on the underside surface of the head.
One problem with magneto-optical (M-O) systems is that the magnetic media is highly durable, requiring extensive heating to create the recorded series of crescent-shaped bit domains. The extensive heating of the media in close proximity to the recording head causes condensation of the media material on the lens of the recording head, clouding the lens so that read and write utility of the lens is obstructed.
What is needed is an apparatus and operating method for avoiding condensation on the lens of a magneto-optical recording system. What is further needed is a fabrication method for constructing a magneto-optical recording head that avoids condensation on the lens.
It has been discovered that a magneto-optical head with a centrally-located solid immersion lens and a coil formed radially about the lens advantageously utilizes an insulating material with a relatively high thermal conductivity for isolating the coil. The high thermal conductivity of the insulating material avoids heat damage to the head when current is passed through the head during a write operation.
It has further been discovered that a magneto-optical head with a centrally-located solid immersion lens and a coil formed radially about the lens is advantageously fabricated using a chemical-mechanical contouring operation for contouring an insulating material with a relatively high thermal conductivity for isolating the coil with no intervening material having a relatively low thermal conductivity separating the high thermal conductivity insulating layer and the coil. The combination of the chemical-mechanical contouring operation and the lack of a low thermal conductivity material effectively produce an insulating layer that is thin but has a contour with a very smooth surface, effectively producing a highly compact multiple-level coil.
In accordance with one aspect of the present invention, a magneto-optical head includes a substrate perforated by a hole, a mesa formed within the hole in the substrate of a material having a high refractory index, and a first coil arranged on the substrate in a first coil layer. The first coil is coiled around the mesa at an increasing radius about the mesa. The magneto-optical head further includes a first high thermal conductivity insulating layer deposited over the substrate around, between, and overlying the first coil with no intervening material having a relatively low thermal conductivity separating the first high thermal conductivity insulating layer and the first coil, the first high thermal conductivity insulating layer having a planar surface. The magneto-optical head has multiple coil layers and thus includes a second coil arranged on the first high thermal conductivity insulating layer in a second coil layer. The second coil is also coiled around the mesa at an increasing radius about the mesa. A second high thermal conductivity insulating layer is deposited over the first high thermal conductivity insulating layer around, between, and overlying the second coil with no intervening material having a relatively low thermal conductivity separating the second high thermal conductivity insulating layer and the second coil. The second high thermal conductivity insulating layer has a planar surface. A via passes through the first high thermal conductivity insulating layer and couples the first coil and the second coil to form a continuous coil in the first and second coil layers.
In some implementations, the magneto-optical head further includes a conductive heating element layer coupled encircling and adhered to lateral sides of the mesa, and having lead appendages extending from the lateral sides of the mesa overlying the substrate and underlying the first coil layer. The magneto-optical heads with the conductive heating element may include an insulative layer coupled between the conductive heating element layer and the first coil layer.
In accordance with another aspect of the present invention,a method of fabricating a magneto-optical head includes supplying a substrate wafer, drilling a hole in the substrate, positioning a sphere of a material having a high refractory index within the hole, machining the substrate and sphere combination to convert the sphere into a mesa, depositing a conductive layer overlying the substrate, and etching the conductive layer to form a coil coiled around the mesa at an increasing radius about the mesa. The method further includes depositing a high thermal conductivity insulating layer over the substrate around, between, and overlying the coil with no intervening material having a relatively low thermal conductivity separating the high thermal conductivity insulating layer and the coil, and chemical-mechanically contouring the high thermal conductivity insulating layer to form a planar surface.
For some implementations of the magneto-optical heads, the method also includes fabricating a finished thin film substrate including a plurality of magneto-optical heads; wherein the operation of chemical-mechanically contouring the high thermal conductivity insulating layer forms a substantially smooth, curved surface overlying ones of the plurality of magneto-optical heads.
For some implementations of the magneto-optical heads, the method further includes depositing a conductive heating element layer directly over the mesa and the substrate, etching the conductive heating element layer to form a conductive heating element coupled encircling and adhered to lateral sides of the mesa, and having lead appendages extending from the lateral sides of the mesa overlying the substrate and underlying the first coil layer, and forming an insulative layer coupled between the conductive heating element layer and the first coil layer, the insulative layer having a thermal conductivity substantially lower than the thermal conductivity of the material forming the first, second, and at least one additional high thermal conductivity insulating layers.